Olsen法测定蔗区土壤有效磷影响因素研究

Influence Factors of Determination for Soil Available Phosphorus by Olsen Method in Sugarcane Planting Region

为了提高蔗区土壤用碳酸氢钠浸提-钼锑抗比色法(简称Olsen法)测定有效磷含量的精密度和检测效率,本文对Olsen法测定土壤样品有效磷时比色皿的选择、浸提温度、浸提土液比、振荡频率和振荡时间等影响因素进行了分析研究,结果显示当样品浓度较小时,应选用光程长度较大的如2、3 cm比色皿,反之,选用光程长度较小的如1 cm比色皿;为保持显色时待测液的酸度,在加入显色剂前,需先调节浸提液的pH至微黄色,以保证实验结果的准确性;选择最大吸收波长700 nm处作为测量波长,以获得较高的灵敏度及较好的线性关系。在土液比1∶20,振荡时间30 min,振荡频率180±20 r/min,浸提温度25±1℃等条件下测定蔗区土壤样品有效磷最为理想,测定土壤样品有效磷含量的RSD为0.41%~1.22%,符合标准要求。与NY/T 1121.7-2014相比,本方法缩短了实验时间,增加了实验结果的稳定性,优化了环境对实验的限制。

In order to improve the detection efficiency and precision of soil available phosphorus content in sugar⁃cane field using sodium bicarbonate leaching-molybdenum antimony colorimetric method(Olsen method),in this paper,the affecting factors such as cuvette,extraction temperature,ratio of soil to liquid,oscillation frequency and oscillation time for the determination of available phosphorus in soil samples by Olsen method were analyzed.The results suggested using cuvette with a larger optical path length,such as 2 or 3 cm for soil samples with lower concentration,and smaller optical path length such as 1 cm for soil samples with greater concentration;The pH of the extract liquor should be maintained within a certain range by adjusted to yellowish before adding the chromogenic agent to ensure the accuracy of the experimental results;The maximum absorption wavelength of 700 nm was selected for obtaining higher sensitivity and better linear relationship.The soil-liquid ratio of 1:20,30 min for oscillation time,oscillation frequency of 180±20 r/min,extraction temperature at 25±1℃were optimum conditions for measurement of effective phosphorus content of cane soil samples,which gage a RSD range of 0.41%-1.22%that met the standard requirements.Compared with standard NY/T 1121.7-2014,this method shortened the experimental time,improved the stability of the experimental results,and relieved the environmental constraints.